Hindering of rotational motion of guest molecules in the Type I clathrate hydrate

► Rotations of both CO and ethylene oxide are hindered in Type I clathrate hydrates. ► Steric effects are responsible for hindering of CO rotations. ► The rotational hindering sharpens and intensifies the C-O stretch band. ► van der Waals interactions hinder ethylene oxide rotations. ► Neither guest-induced H-bonds nor L-defects are formed below 110 K.